Transfer track stopper for packaged integrated circuits

ABSTRACT

A packaged integrated circuit transfer track with a stopper arm that is constrained to vertical motion. A packaged integrated circuit transfer track with a cam follower that engages a cam causing a stopper arm to raise or lower vertically. A packaged integrated circuit transfer track with an actuator that engages a switch causing a motor or solenoid to raise or lower the stopper arm vertically.

FIELD

This disclosure relates to the field of integrated circuits. Moreparticularly, this disclosure relates to a transfer track for packagedintegrated circuits.

BACKGROUND

Transfer tracks are used to transfer packaged integrated circuits toequipment such as integrated circuit testing equipment, integratedcircuit inspection equipment, and circuit board assembly equipment.

A typical transfer track is illustrated in FIG. 1A.

The transfer track consists of a transfer track rail 100 with a trackslot 102 in which packaged integrated circuits 122 such as QFN(Quad-Flat No leads) packaged integrated circuits, are placed end-to-endin a row.

A transfer track head 104 with a packaged IC slot 105 of sufficient sizeto receive one packaged IC 122 alternatively engages and disengages withthe transfer track rail 100 during the packaged IC 122 transferoperation. A tab 106 on the transfer track head 104 mates with anopening 107 in the lead end of the transfer track rail 100 to ensureproper alignment of the packaged IC slot 105 with the transfer trackslot 102 during engagement.

A stopper arm 118 with a cam 114 is attached to the transfer track rail100 with a pivot 116. A stopper 108 attached to the upper end of thestopper arm 118 presses down on the lead packaged IC 122 at the lead endof the transfer track rail 100 to prevent it from moving when thetransfer track head 104 disengages and reengages with the transfer trackrail 100.

A transfer head arm 110 with a cam follower 112 is attached to thetransfer head 104. As the transfer head 104 engages and disengages withthe transfer track rail 100 the cam follower 112 actuates the cam 114causing the stopper arm 118 to to clamp and unclamp the lead packaged IC122.

The major steps in the operation of the transfer track are illustratedin FIGS. 1A through 1F.

As shown in FIG. 1A, the lead packaged IC 122 is clamped in place by thestopper 108 attached to the upper end of the stopper arm 118 when thetransfer head 104 is disengaged from the transfer rail 100.

In FIG. 1B, the transfer track head 104 mates with the transfer track100. As the transfer head 104 mates with the transfer track 100, the camfollower 112 on the transfer head arm 110 actuates the cam 114 on thestopper arm 118 causing the stopper arm 118 to pivot. The pivotingmotion causes the stopper 108 to lift up and to unclamp the leadpackaged IC 122.

As is illustrated in FIG. 1C the packaged ICs 112 are then advancedalong the transfer track slot 102 causing the lead packaged ICs 112 tobe transferred from the transfer track slot 102 on the transfer track100 to the packaged IC slot 105 on the transfer head 104.

In FIG. 1D, the transfer head 104 now containing the lead packaged IC122 in the packaged IC slot 105 disengages from the transfer rail 100.As the transfer head 104 disengages from the transfer rail 100, the camfollower 112 on the transfer head arm 110 separates from the cam 114 onthe stopper arm 118 causing the stopper arm 118 to pivot so that thestopper 108 clamps down on the packaged IC 122 that now occupies thelead position in the transfer track slot 102.

A pick-up tip 120 then picks up the packaged IC 122 from the transferhead 104 as illustrated in FIGS. 1E and 1F.

After the packaged IC 122 is transferred to the equipment, the transfertrack 100 is ready to repeat the process and to transfer the nextpackaged IC 122 to the equipment.

SUMMARY

The following presents a simplified summary in order to provide a basicunderstanding of one or more aspects of the invention. This summary isnot an extensive overview of the invention, and is neither intended toidentify key or critical elements of the invention, nor to delineate thescope thereof. Rather, the primary purpose of the summary is to presentsome concepts of the invention in a simplified form as a prelude to amore detailed description that is presented later.

A packaged integrated circuit transfer track with a stopper arm that isconstrained to vertical motion. A packaged integrated circuit transfertrack with a cam follower that engages a cam causing a stopper arm toraise or lower vertically. A packaged integrated circuit transfer trackwith an actuator that engages a switch causing a motor or solenoid toraise or lower the stopper arm vertically.

DESCRIPTION OF THE VIEWS OF THE DRAWINGS

FIG. 1A-1F (Prior art) illustrates the operation of a packagedintegrated circuit transfer track.

FIG. 2A-2F illustrates the operation of an embodiment packagedintegrated circuit transfer track.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Embodiments of the disclosure are described with reference to theattached figures. The figures are not drawn to scale and they areprovided merely to illustrate the disclosure. Several aspects of theembodiments are described below with reference to example applicationsfor illustration. It should be understood that numerous specificdetails, relationships, and methods are set forth to provide anunderstanding of the disclosure. One skilled in the relevant art,however, will readily recognize that the disclosure can be practicedwithout one or more of the specific details or with other methods. Inother instances, well-known structures or operations are not shown indetail to avoid obscuring the disclosure. The embodiments are notlimited by the illustrated ordering of acts or events, as some acts mayoccur in different orders and/or concurrently with other acts or events.Furthermore, not all illustrated acts or events are required toimplement a methodology in accordance with the present disclosure.

An embodiment transfer track with an improved stopper arm 218 is shownin FIG. 2A.

The embodiment transfer track consists of a transfer track rail 200 witha track slot 202 in which packaged integrated circuits 222 such as QFN(Quad-Flat No leads) packaged integrated circuits, are placed in a row.

A transfer track head 204 with a packaged IC slot 205 of sufficient sizeto receive one packaged IC 222 alternatively engages and disengages withthe transfer track rail 200 during the packaged IC 212 transferoperation. A tab 206 on the transfer track head 204 mates with anopening 207 in the lead end of the transfer track rail 200 to ensureproper alignment of the packaged IC slot 205 with the transfer trackslot 202 during engagement.

A stopper arm 218 attached to the transfer track rail 200 movesvertically but not horizontally. A stopper 208 attached to the upper endof the stopper arm 218 clamps down on the lead packaged IC 222 at thelead end of the transfer track rail 200 to prevent the packaged IC 222from moving when the transfer track head 204 disengages and reengagesfrom the transfer track rail 200. A transfer head arm 210 with a camfollower 212 is attached to the transfer head 204. The cam follower 212may contact a cam 214 on the stopper arm 218 to mechanically move thestopper arm 218 in a vertical direction. Alternatively the cam follower212 may be an actuator that trips a switch on the stopper arm 218causing a motor or solenoid to move the stopper arm 218 vertically.

The motion of the stopper arm 218 in the embodiment transfer track isconstrained to be vertical. This ensures that no horizontal force isapplied to the packaged IC 222 when the stopper 208 clamps or unclampsthe lead packaged IC 222. The typical stopper arm 118 (FIG. 1A) whichpivots during clamping and unclamping of the lead packaged IC 122, mayapply horizontal force to the lead packaged IC 122 causing it to movehorizontally while the stopper 108 is applying downward pressure. Thismay cause the contact pads on the packaged IC to be scratched anddamaged. Soldered connections to these damaged contact pads may be weakand unreliable resulting in either immediate circuit failure or circuitfailure during use. One typical transfer track was found to produce over500,000 ppm failures due to scratched contact pads.

The major steps in the operation of the embodiment transfer track isillustrated in FIGS. 2A through 2F.

As shown in FIG. 2A, the lead packaged IC 222 is clamped in place by thestopper 208 attached to the upper end of the stopper arm 218. In FIG.2A, the transfer head 204 with its attached transfer head arm 210 isdisengaged from the transfer rail 200.

In FIG. 2B, the transfer track head 204 mates with the transfer trackrail 200. As the transfer head 204 mates with the transfer track rail200, the actuator 212 on the transfer head arm 210 contacts the cam orswitch 214 on the stopper arm 218 causing the stopper arm 218 to move upvertically and to unclamp the lead packaged IC 222.

As is illustrated in FIG. 2C the packaged ICs 222 are then advancedalong the transfer track slot 202 so that the lead packaged IC 222 istransferred from the transfer track slot 202 in the lead end of thetransfer track rail 200 to the packaged IC slot 205 on the transfer head204.

In FIG. 2D, the transfer head 204 with the lead packaged IC 222 in thepackaged IC slot 205 disengages from the transfer track rail 200. As thetransfer head 204 disengages from the transfer track rail 200, theactuator 212 on the transfer head arm 210 disengages from the cam orswitch 214 on the stopper arm 218 causing the stopper arm 218 to lowervertically so that the stopper 208 clamps the packaged IC 222 that nowoccupies the lead position in the transfer track slot 202. Since themotion of the stopper arm 218 is constrained to vertical motion only, nohorizontal motion of the package IC which may damage the contact pads onthe packaged IC 222 occurs.

As shown in FIGS. 2E and 2F, a pick-up head 220 then picks up thepackaged IC 222 from the transfer head and transfers it to theequipment.

After the packaged IC 222 is transferred to the equipment, the transfertrack is ready to repeat the process and to transfer the next packagedIC 222 to the equipment.

The embodiment transfer track with vertical stopper motion providessignificant advantages and cost savings. The packaged integratedcircuits that are transferred using the transfer track have a highvalue. The integrated circuit manufacturing process that produces the ICchip is a lengthy and expensive process. The packaging process is alsoexpensive and may double the cost of the packaged IC. Only integratedcircuits that have been tested and known to be good are packaged.Scrapping integrated circuits that are known to be good and have beenpackaged is a very costly place to produce scrap. A typical transfertrack produced over 500,000 ppm scrap due to scratched lead pads causedby horizontal scraping of the packaged IC against the transfer trackslot while under pressure from the stopper. Implementation of theembodiment transfer track for a period that exceeded 6 months completelyeliminated the scrap caused by stopper scratches.

Testing has shown that the vertical motion stopper can operate with 6times lower force than the angular motion stoppers that pivot. Thissignificantly reduces damage to the contact pads. Unlike the angularmotion stoppers that pivot, the stopping down force on the packaged ICusing the embodiment transfer track remains constant even after extendeduse.

In addition, as soon as scratched lead pads are detected, the transfertrack is shut down and remains down until stopper parts are replaced andadjustments are made to eliminate the scratching. Typically the transfertrack is down for 3 hours or more to replace parts and make adjustments.The embodiment transfer track reduces transfer track down time by morethan 12.5% significantly reducing operating cost.

While various embodiments of the present disclosure have been describedabove, it should be understood that they have been presented by way ofexample only and not limitation. Numerous changes to the disclosedembodiments can be made in accordance with the disclosure herein withoutdeparting from the spirit or scope of the disclosure. Thus, the breadthand scope of the present disclosure should not be limited by any of theabove described embodiments. Rather, the scope of the disclosure shouldbe defined in accordance with the following claims and theirequivalents.

What is claimed is:
 1. An integrated circuit transfer track, comprising:a transfer track rail with a stopper arm wherein motion of the stopperarm is constrained to be vertical; a cam on the stopper arm; and atransfer track head with a cam follower wherein the cam follower is incontact with the cam on the stopper arm when the transfer track head iscoupled with the transfer track rail and the stopper arm is raisedvertically unclamping a packaged integrated circuit from the transfertrack rail and wherein the cam follower is not in contact with the camwhen the transfer head is uncoupled from the transfer track rail and thestopper arm is lowered vertically clamping the packaged integratedcircuit against the transfer track rail.
 2. The integrated circuittransfer track of claim 1 further comprising: a switch on the stopperarm; a transfer track head with an actuator wherein the actuator is incontact with the switch on the stopper arm when the transfer track headis coupled with the transfer track rail and the switch actuates a motorso that the stopper arm is raised vertically unclamping a packagedintegrated circuit from the transfer track rail and wherein the actuatorceases contact with the switch when the transfer head is uncoupled fromthe transfer track rail and the stopper arm is lowered verticallyclamping the packaged integrated circuit against the transfer trackrail.
 3. An integrated circuit transfer track, comprising: a transfertrack rail with an opening; a transfer track head with a tab that mateswith the opening when the transfer track head is coupled with thetransfer track rail; a stopper arm with a cam wherein the stopper arm isattached to the transfer track rail and wherein motion of the stopperarm is constrained to be vertical; a transfer track head arm attached tothe transfer track head and a cam follower attached to the transfertrack head arm; the cam follower in contact with the cam when thetransfer track head is coupled with the transfer track rail and thestopper arm is in an up position; and the cam follower is not in contactwith the cam when the transfer track head is uncoupled from the transfertrack rail and the stopper arm is in a down position.
 4. An integratedcircuit transfer track, comprising: a transfer track rail with anopening; a transfer track head with a tab that mates with the openingwhen the transfer track head is coupled with the transfer track rail; astopper arm with a switch wherein the stopper arm is attached to thetransfer track rail and wherein motion of the stopper arm is constrainedto be vertical; a transfer track head arm attached to the transfer trackhead and an actuator attached to the transfer track head arm; theactuator in contact with the switch when the transfer track head iscoupled with the transfer track rail and the stopper arm is in an upposition; and the actuator is not in contact with the switch when thetransfer track head is uncoupled from the transfer track rail and thestopper arm is in a down position.
 5. The integrated circuit transfertrack of claim 4 further comprising the switch coupled to a motor thatraises and lowers the stopper arm.
 6. The integrated circuit transfertrack of claim 4 further comprising the switch coupled to a solenoidthat raises and lowers the stopper arm.
 7. An integrated circuittransfer track, comprising: a transfer track rail with a stopper armwherein motion of the stopper arm is constrained to be vertical a switchon the stopper arm; and a transfer track head with an actuator whereinthe actuator is in contact with the switch on the stopper arm when thetransfer track head is coupled with the transfer track rail and theswitch actuates a motor so that the stopper arm is raised verticallyunclamping a packaged integrated circuit from the transfer track railand wherein the actuator ceases contact with the switch when thetransfer head is uncoupled from the transfer track rail and the stopperarm is lowered vertically clamping the packaged integrated circuitagainst the transfer track rail.